Adjustable curve ruler



May 21, 1935. w, s WESTQN 2,001,949

ADJUSTABLE CURVE RULER Filed May 12, 1954 2 Sheets-Sheet 1 William 5. Weston ,eymzv fiw A figs.

l atented May 21, 1935 i g V UNITED STATES PATENT. OFFICE i 1 2,001,949 I l g r ADJUSTABLE cURvE nuLER Williams. Weston, Douglaston, N. Y. Application May 12, 1934, Serial 1I o. 'l25 ,285, 2 Claims. 01. 33-177) The invention relates to an adjustable ruler of my improved instrument, I utilize two pair of for the use of draftsmenand others when drawthese fundamental points. g ing or checking curves of either short or long Referring now to the'geometric illustrations, radii, under conditions when the use of an ordi- Figs! and 5,the line A represents the flexible 5 nary drafting compass, or beam compass, is 1111- member of the instrument with its ends indicated 5 practicable. It comprises a flexible arc member by the lettersPC and BT;-these letters being of constant length; rigid end frames or members commonly used by engineers and draftsmen to attached to the ends of the arc member and mark the two ends of-a curve. At each end the provided with edges or other means for indicatlines T and Rarepresent edges carried by the 1 ing or defining lines that are tangent and radial rigid end membersand held tangent and radial 10 respectively to the arc member at the ends theretothecurve of the flexible member at the ends of and a set of bars pivotally connecting the. C nd T-" In the following p Q i 116 rigid end frames and arranged to hold the ends lettersPC and PT are usedto d gnate the end or tangent points of the flexible arc member at member s. 'I'he-two pair of fundamenta points the correct distance apart and the tangent and are ind cated by t e l t r 03 14 and 04 Is, the 15 radial line indicating means in correct relation same as" shown in Fig-8 of Patent 1,893,689. to the arc member when the latter is flexed to Fora flexible arc member "7.854 units long, the any desired radius. fixed location of the points relative the adjacent My presentinvention is a curve ruler utilizing PC or PT and tangent Tisgivenin-Fig. 4. The

0-, the fundamental principle of construction and distance apart for the points of each pair is 4.5 operation disclosed in my Patent No. 1,893,689, units. remaining constant when the flexible issued January 10, 1933; and is also a modificamember is curved tothearc of a circle like that tion of the ruler for drawing" arcs of circles diswn in F 5. n my pr s nt c nstru ti n closed in my Patent No. 1,953,282, issued April i ad f np tine thes poin s d t, s lus- 3rd, 1934. The invention is hereinafter more trated by full lines in Figs. .4 and 5, I use a par- 25 fully described, illustrated in the accompanying a l l gifamfi bar h ld in. parallel relation to drawings, and the novel features more particu t e n corme inethe' p n t ea h air larly pointed out in the appended claims. fu m n al p n The tWO Paralleldgrams a e Referring to the drawings: illustrat d by. full lines in Fi 5 a d 'A Fig. 1 is a plan view of the instrument with the mp r ant detail gove ni .ithe Construction of so arc member in the straight line position; 1 h parallelogramsis thelocation of the pivot Fig. 2 is a plan view of the instrument with poin D, constitutingthe intermediate connection the arc member flexed to an arc of a circle be w n i O Y a e m. The po t D through an angle of 90 degrees, is located' half ,yvay between the fundamental 5 Fig. 3 is a cross section on the line 3-3 of D t B nd 1 50 iline through-those Fig. 1. i v points forall positionsof adjustment. A point Figs. 4 to 7, inclusive, are geometric illustra- C1 used in determining the. location of some of tions used to describe the fundamental facts h P ot p t is Q d half y b tw engoverning the. construction and relation of the fundamental P i 03 and 13011 a a h l ne flexible'arc member, the rigid end members, and through those Point h Similarly 40 v the pivotal connections between the end memlocated between Points. 04 and 141 A linewfmml bers, as embodied in the com le e instrument 0 C1 to is Par l l W th and, equal to half the Figs and p t f length of the line connecting fundamental points v O3 and 14 for all positions of adjustment. This The design of my adiustable curve ruler is m based on the fact that, in a curve ruler having 15 also'tru'e for the lme C2 D parallel wlth the 45 lineoi Is. For an instrument in which the line. a flexible curve member of constant length with connecting the points" each pair of funda rigid end members f the end s,thereof" mental points is 4.5.units long, as shown in Fig. there are a series of points in fixed position rela- 43 the length of the parallel lines. C1 D and C2 D tive to one end member, each of which may be would be 1 paired with and held at constant distance from The parallelograms are constructed in para difierentpoint n a ries Of Points Which are allelogram'relation to'the lines& D andCz D rein a fixed position relative to the other end memspectively with two sides necessarily equal in her, when the flexible member is adjusted to an length to those lines.

I are of a circle. As a basis for the construction Referring to the parallelogram at the PC end 55 of the instrument: Pivot points G1 H1 constituting the outer end are in fixed positions on the end member and are in line with the point C1. Pivot points E1 J1 constituting the inner end of the parallelogram are made on a bar which is extended to the point D where it is pivotally connected with a similar extension of the bar of the parallelogram at the PT end. The bars DE1 and DEz are of equal length. The bars H1 J1 and G1 E1 are parallel with and equal in length to the theoretical line C1 D. It maybe noted that the bar H1 J1 could be moved up to and mounted on the line C1 D. The objection to that location is that pivot H1 located at C1 would be in the way of the flexible member for a short radius curve like that of Fig. 7. The parallelogram at the PT end is a duplicate in reverse of the PC end parallelogram, as indicated by the same letters with the sub-numeral 2.

An important novel detail in the construction of my improved instrument may now be described. To hold the intermediate pivot point D, connecting the two parallelograms, in line with thefundamental points, Is and Ir I provide means for holding pivot points E1 and E2 of the two parallelograms in line with a fixed point on each end member, points F1 and F2. The line through these points is a straight line parallel with the line throughpoints I314 and pivot point D. The point F1 is so located on the PC member that the line between points I3 and F1 is equal in length and parallel with the bar DE1. On the PT member point F2 is so located that-line I4 F2 is also equal in length and parallel with the bar DE2. As a result of this construction the pivot point D is held in a straight line and at equal distances from the points Is and I4 for all angular movements of the parallelograms in the adjustments of the flexible member of arcs'of circles.

- Referring now to Fig. 1, the means provided for holding points F1 F2 and pivot points E1 E2 in a straight line is a flat bar K with slots for the E1 E2 pivot points and for a bolt at point F2 on the PT end member, permitting all four points to be moved toward each other in' the process of adjusting the instrument from the straight position of Fig. l is that for an arc of a circle like that of Fig. 2; The end of the bar at the point F1 on the PC end has a pivotal connection only. When the instrument'is adjusted to the desired curvature, theadjustment is held by means ofa clamp nut'on the boltat point F2. A plate L carried by the bolt is marked with an arrow point which indicates by means of a scale drawn on the 1 bar K the radius of the curve to'which the instrument is adjusted. For an arc member 7.854

. units long curved through'90 degrees, the radius would be 5, as shown in Fig. 2. Fora larger instrument the radius for any angle would be proportionally longer. The scale which would also be longer could be marked much finer than shown in Figs. 1 and2. The bar K may be termed a base element utilized in the control of the pivotal relation between the end members.

It is to be noted that, with the bars DE1 and DE; equal in length, their angles with the straight guide bar K continue to be equal when shifted from the position in Fig. 1 toward the position of Fig. 2. Because of that fact and the parallelogram relation of the end members. to those bars, the angular relation of the end members with the bar K also remains equal.

In the construction of the instrument based on the fundamental points and dimensions shown in Fig. 4 the following procedure may be followed: Referring to the PC end in Fig. 6, the pivot points G1 and H1 are located on the frame in line with the point C1, the distance between these points being optional. The choice in the location of the points G1 and H1 also determines the length of the bar E1 J1 D and the relative location of its pivot points, because the bars H1 J1 and G1 E1 connecting the bar E1 J1 D with the frame are equal in length and parallel to the line C1 D. The pivot point F1 is located on the frame on a line through the point G1 parallel with the line C1 I3 and at a distance from G1 equal to the distance between the points C1 and I3. It will be apparent that the triangle formed by the pivot points G1 F1 E1 is identical in angles and dimensions with the triangle formed by the fundamental points C1 I3 D; and that the third side F1 E1 of one will be parallel with the third side I3 D of the other, for all positions of adjustment.

The pivot points on the PT end frame are located' at the same relative distance and position as" on the PC end, but in the reverse direction.

Because of the fact that with the instrument ad' points shown in Fig. 4, which govern the location of the pivot points. I may use another set of fundamental points, for example, like those used in the construction of the instrument illustrated in Patent 1,893,689, and specifically pointed out in thegeometric diagram of Fig. 7 in that patent.

I'clarm as my invention:

1. An adjustable curve ruler for drawing arcs of circles comprising a flexible arc member of constant length, end members rigidly attached to the ends of the arc member, a set of six bars pivotally connected together and to the end members, each end member together with three of said bars forming through the pivotal connections a parallelogram, and means in combination with said parallelograms for controlling the relative angular movements at said pivotal connections whereby the said end members are held at the correct angle and the correct distance apart with the flexible arc member curved to an arc of a circle.

' 2. An adjustable curve ruler for drawing arcs of circles comprising a flexiblearc member of constant length, end members rigidly attached to the ends of the are member, a base'element, said end members being-pivoted to said base element, parallel link pairs respectively connected to said end members and connected to each other for unitary pivotal movement relative to each other about a common pivot axis, the pivotal connection between one of said end members and the base element being adjustable toward and from the pivotal connection between the other end member and the base element, and means for locking the ruler in adjusted position.

WILLIAM S. \VESTON. 

